Communication systems tend to be open loop, available to a wide number of users, and hence are not secure. For example, telephone and computer network systems, particularly the Internet, are vulnerable to hacking and disruptions by hostile entities. Even institutions which take precautions to avoid such disruptions to their computer systems, for example by duplicating their computer systems on a remote “offsite” location, still are vulnerable to further disruption due to their reliance on open loop communication systems.